[llvm-branch-commits] [llvm] 10955ea - Revert "[ARM] Use .reloc for weak symbols in PIC mode instead of GOT indirect…"
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llvm-branch-commits at lists.llvm.org
Sat Jul 11 16:35:58 PDT 2026
Author: Tony Guillot
Date: 2026-07-12T01:35:54+02:00
New Revision: 10955eac1c053d58bbcda3d86912deee43ffc798
URL: https://github.com/llvm/llvm-project/commit/10955eac1c053d58bbcda3d86912deee43ffc798
DIFF: https://github.com/llvm/llvm-project/commit/10955eac1c053d58bbcda3d86912deee43ffc798.diff
LOG: Revert "[ARM] Use .reloc for weak symbols in PIC mode instead of GOT indirect…"
This reverts commit 290279b6b69138f4162cace4865713efa12ec262.
Added:
Modified:
llvm/lib/Target/ARM/ARMAsmPrinter.cpp
llvm/lib/Target/ARM/ARMFastISel.cpp
llvm/lib/Target/ARM/ARMISelLowering.cpp
llvm/lib/Target/ARM/ARMSubtarget.cpp
llvm/lib/Target/ARM/ARMTargetMachine.h
llvm/test/CodeGen/ARM/elf-preemption.ll
llvm/test/CodeGen/ARM/weak-hidden-pic.ll
Removed:
################################################################################
diff --git a/llvm/lib/Target/ARM/ARMAsmPrinter.cpp b/llvm/lib/Target/ARM/ARMAsmPrinter.cpp
index b7448dd5c9783..c25a2cfeff8d6 100644
--- a/llvm/lib/Target/ARM/ARMAsmPrinter.cpp
+++ b/llvm/lib/Target/ARM/ARMAsmPrinter.cpp
@@ -1016,36 +1016,6 @@ void ARMAsmPrinter::emitMachineConstantPoolValue(
unsigned char TF =
TM.getTargetTriple().isOSBinFormatMachO() ? ARMII::MO_NONLAZY : 0;
MCSym = GetARMGVSymbol(GV, TF);
-
- // For weak symbols in ELF PIC mode, the assembler would eagerly resolve a
- // PC-relative expression like sym-(LPC+8) when the symbol and reference are
- // in the same section, preventing the linker from overriding a weak
- // definition with a non-weak definition from another section. Use a
- // .reloc directive rather than a fixup to force the generation of a
- // relocation (R_ARM_REL32) so the linker can perform the override.
- if (GV->isWeakForLinker() && TM.getTargetTriple().isOSBinFormatELF() &&
- TM.isPositionIndependent() && ACPV->getPCAdjustment() != 0) {
- MCSymbol *CPILabel = OutContext.createTempSymbol();
- OutStreamer->emitLabel(CPILabel);
- // Emit local-only expression: CPILabel - (LPC+PCAdj)
- const MCExpr *LocalExpr = MCSymbolRefExpr::create(CPILabel, OutContext);
- MCSymbol *PCLabel =
- getPICLabel(DL.getInternalSymbolPrefix(), getFunctionNumber(),
- ACPV->getLabelId(), OutContext);
- const MCExpr *PCRelExpr = MCSymbolRefExpr::create(PCLabel, OutContext);
- PCRelExpr = MCBinaryExpr::createAdd(
- PCRelExpr,
- MCConstantExpr::create(ACPV->getPCAdjustment(), OutContext),
- OutContext);
- LocalExpr = MCBinaryExpr::createSub(LocalExpr, PCRelExpr, OutContext);
- OutStreamer->emitValue(LocalExpr, Size);
- // Emit .reloc to force linker resolution of the weak symbol.
- const MCExpr *CPIExpr = MCSymbolRefExpr::create(CPILabel, OutContext);
- const MCExpr *SymExpr = MCSymbolRefExpr::create(MCSym, OutContext);
- OutStreamer->emitRelocDirective(*CPIExpr, "R_ARM_REL32", SymExpr,
- SMLoc());
- return;
- }
} else if (ACPV->isMachineBasicBlock()) {
const MachineBasicBlock *MBB = cast<ARMConstantPoolMBB>(ACPV)->getMBB();
MCSym = MBB->getSymbol();
diff --git a/llvm/lib/Target/ARM/ARMFastISel.cpp b/llvm/lib/Target/ARM/ARMFastISel.cpp
index 2c5d286e11c4f..1cf0d98f690aa 100644
--- a/llvm/lib/Target/ARM/ARMFastISel.cpp
+++ b/llvm/lib/Target/ARM/ARMFastISel.cpp
@@ -3033,7 +3033,8 @@ bool ARMFastISel::tryToFoldLoadIntoMI(MachineInstr *MI, unsigned OpNo,
}
Register ARMFastISel::ARMLowerPICELF(const GlobalValue *GV, MVT VT) {
- bool UseGOT_PREL = !GV->isDSOLocal();
+ // Weak symbols need GOT indirection even when hidden/DSO-local.
+ bool UseGOT_PREL = !GV->isDSOLocal() || GV->isWeakForLinker();
LLVMContext *Context = &MF->getFunction().getContext();
unsigned ARMPCLabelIndex = AFI->createPICLabelUId();
unsigned PCAdj = Subtarget->isThumb() ? 4 : 8;
diff --git a/llvm/lib/Target/ARM/ARMISelLowering.cpp b/llvm/lib/Target/ARM/ARMISelLowering.cpp
index 28d4c0ff22703..35c46c3f0a75a 100644
--- a/llvm/lib/Target/ARM/ARMISelLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMISelLowering.cpp
@@ -3651,10 +3651,15 @@ SDValue ARMTargetLowering::LowerGlobalAddressELF(SDValue Op,
return V;
if (isPositionIndependent()) {
- SDValue G = DAG.getTargetGlobalAddress(
- GV, dl, PtrVT, 0, GV->isDSOLocal() ? 0 : ARMII::MO_GOT);
+ // Weak symbols need GOT indirection even when hidden/DSO-local.
+ // The assembler eagerly resolves PC-relative expressions when the
+ // symbol and reference are in the same section, which prevents the
+ // linker from overriding a weak definition with a non-weak one.
+ bool UseGOT = !GV->isDSOLocal() || GV->isWeakForLinker();
+ SDValue G = DAG.getTargetGlobalAddress(GV, dl, PtrVT, 0,
+ UseGOT ? ARMII::MO_GOT : 0);
SDValue Result = DAG.getNode(ARMISD::WrapperPIC, dl, PtrVT, G);
- if (!GV->isDSOLocal())
+ if (UseGOT)
Result =
DAG.getLoad(PtrVT, dl, DAG.getEntryNode(), Result,
MachinePointerInfo::getGOT(DAG.getMachineFunction()));
diff --git a/llvm/lib/Target/ARM/ARMSubtarget.cpp b/llvm/lib/Target/ARM/ARMSubtarget.cpp
index 4893d8d3a9ef1..0f324a6a31757 100644
--- a/llvm/lib/Target/ARM/ARMSubtarget.cpp
+++ b/llvm/lib/Target/ARM/ARMSubtarget.cpp
@@ -397,7 +397,8 @@ bool ARMSubtarget::isGVIndirectSymbol(const GlobalValue *GV) const {
}
bool ARMSubtarget::isGVInGOT(const GlobalValue *GV) const {
- return isTargetELF() && TM.isPositionIndependent() && !GV->isDSOLocal();
+ return isTargetELF() && TM.isPositionIndependent() &&
+ (!GV->isDSOLocal() || GV->isWeakForLinker());
}
unsigned ARMSubtarget::getMispredictionPenalty() const {
diff --git a/llvm/lib/Target/ARM/ARMTargetMachine.h b/llvm/lib/Target/ARM/ARMTargetMachine.h
index 215b541620acb..109d6fd5e6671 100644
--- a/llvm/lib/Target/ARM/ARMTargetMachine.h
+++ b/llvm/lib/Target/ARM/ARMTargetMachine.h
@@ -111,6 +111,15 @@ class ARMBaseTargetMachine : public CodeGenTargetMachineImpl {
(GV->isDeclarationForLinker() || GV->hasCommonLinkage()))
return true;
+ // In ELF PIC mode, weak symbols referenced via the constant pool use a
+ // PC-relative expression (e.g. .long xxx-(.LPC+8)) that the assembler
+ // eagerly resolves when both the symbol and label are in the same section.
+ // This prevents the linker from overriding a weak definition with a
+ // non-weak one. Use GOT indirection for weak symbols to avoid this.
+ if (getTargetTriple().isOSBinFormatELF() && isPositionIndependent() &&
+ GV->isWeakForLinker())
+ return true;
+
return false;
}
diff --git a/llvm/test/CodeGen/ARM/elf-preemption.ll b/llvm/test/CodeGen/ARM/elf-preemption.ll
index 6d5a78dd95aa4..88b35683b97c0 100644
--- a/llvm/test/CodeGen/ARM/elf-preemption.ll
+++ b/llvm/test/CodeGen/ARM/elf-preemption.ll
@@ -59,14 +59,13 @@ define ptr @get_weak_dsolocal_var() nounwind {
; PIC: @ %bb.0:
; PIC-NEXT: ldr r0, .LCPI2_0
; PIC-NEXT: .LPC2_0:
-; PIC-NEXT: add r0, pc, r0
+; PIC-NEXT: ldr r0, [pc, r0]
; PIC-NEXT: bx lr
; PIC-NEXT: .p2align 2
; PIC-NEXT: @ %bb.1:
; PIC-NEXT: .LCPI2_0:
; PIC-NEXT: .Ltmp1:
-; PIC-NEXT: .long .Ltmp1-(.LPC2_0+8)
-; PIC-NEXT: .reloc .Ltmp1, R_ARM_REL32, weak_dsolocal_var
+; PIC-NEXT: .long weak_dsolocal_var(GOT_PREL)-(.LPC2_0+8-.Ltmp1)
ret ptr @weak_dsolocal_var
}
@@ -164,14 +163,13 @@ define weak dso_local ptr @weak_dsolocal_func() nounwind {
; PIC: @ %bb.0:
; PIC-NEXT: ldr r0, .LCPI7_0
; PIC-NEXT: .LPC7_0:
-; PIC-NEXT: add r0, pc, r0
+; PIC-NEXT: ldr r0, [pc, r0]
; PIC-NEXT: bx lr
; PIC-NEXT: .p2align 2
; PIC-NEXT: @ %bb.1:
; PIC-NEXT: .LCPI7_0:
; PIC-NEXT: .Ltmp3:
-; PIC-NEXT: .long .Ltmp3-(.LPC7_0+8)
-; PIC-NEXT: .reloc .Ltmp3, R_ARM_REL32, weak_dsolocal_func
+; PIC-NEXT: .long weak_dsolocal_func(GOT_PREL)-(.LPC7_0+8-.Ltmp3)
ret ptr @weak_dsolocal_func
}
diff --git a/llvm/test/CodeGen/ARM/weak-hidden-pic.ll b/llvm/test/CodeGen/ARM/weak-hidden-pic.ll
index 26a779f2dc9f9..4d6eca77af855 100644
--- a/llvm/test/CodeGen/ARM/weak-hidden-pic.ll
+++ b/llvm/test/CodeGen/ARM/weak-hidden-pic.ll
@@ -2,20 +2,18 @@
; RUN: llc < %s -mtriple=thumbv7-linux-gnueabi -relocation-model=pic | FileCheck %s
; RUN: llc < %s -O0 -fast-isel-abort=2 -mtriple=armv7-linux-gnueabi -relocation-model=pic | FileCheck %s
-; Weak dso_local hidden functions must be overridable at link time
-; (a non-weak definition in another object should override the weak one).
-; Instead of using GOT indirection, we use a PC-relative constant pool
-; entry with a .reloc directive to force the assembler to emit a proper
-; relocation (R_ARM_REL32), preventing eager resolution when the symbol
-; and reference are in the same section.
+; Hidden weak function with dso_local must still use GOT indirection
+; in PIC mode on ARM. The assembler eagerly resolves PC-relative
+; expressions like .long xxx-(.LPC+8) when both are in the same section,
+; which prevents the linker from overriding the weak definition with
+; a non-weak one from another object file.
define weak dso_local hidden void @weak_hidden_func() {
ret void
}
; CHECK-LABEL: weak_hidden_func_addr:
-; CHECK: .long .Ltmp{{[0-9]+}}-(.LPC{{[0-9]+}}_0+{{[48]}})
-; CHECK: .reloc .Ltmp{{[0-9]+}}, R_ARM_REL32, weak_hidden_func
+; CHECK: .long weak_hidden_func(GOT_PREL)
define i8* @weak_hidden_func_addr() {
ret i8* bitcast (void()* @weak_hidden_func to i8*)
}
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